Knowledge as to the depth to which the reefs descend has been slowest in accumulating. When the outcrops were first worked in the central section, it was believed that there was little or no gold in the lower levels. Since 1898, however, deep and yet deeper depths have been explored, especially in following the richer reefs, and always with the similar result of meeting with the same, or a superior, grade of ore contents peculiar to the higher sections of the particular reef, so that the inference is strengthened to certainty that profitable exploitation is only limited to the ultimate depth at which modern mining can be carried on. The problem, therefore, is one for the engineers; for, apart from the increased temperature in the lower levels, which can be met by roomier shafts, and the occurrence of water, which is likewise capable of being dealt with, the only difficulty to be met with is that concerned with the hoisting appliances for such enormous depths. So recently as May last the London Chamber of Mines, and more recently the Johannesburg Association of Mining Engineers, were engaged on the solution of this question. It is needless to anticipate the results of their deliberations, the point turning upon the choice betwixt two systems, only so far as to state that means for solving the difficulties of the task are considered to be available, at least, to such depths as 5565 feet on the slope, and that the results of mining at these great depths can be made to show a substantial profit. It may be added, however, that in consequence of the increased cost to reach the ore, the need for the utmost reduction of working costs becomes paramount. The circumstances of gold-mining on the Rand have, therefore, features quite distinct from those of quartz-reef, alluvial, or other kinds of mining, and approximate to those of coal winning, especially in the matter of the depth and regularity of the conglomerate formation. Its peculiarities have created a method of mining, the outcome of costly experiment, experience, and skill, which will remain a lasting asset to future ages.